A controller at a custom cabinet shop quotes a kitchen at $28,000 using last year's overhead rate. Six months later, margin on the job is negative $3,400. The job did not lose money because the materials estimate was wrong; it lost money because the rate misallocated three hours of CNC programming and a setup the bidder never priced. The exam tests whether you can pick the costing method that matches the production environment, and read the variance the result will produce.
HIGH-FREQUENCY: Every managerial answer starts by classifying the cost. Four axes, all testable.
Direct vs indirect. A cost is direct if it can be traced to a cost object economically. Lumber on a specific cabinet, the welder's wages on a specific job, the testing technician on a specific batch. Indirect costs benefit multiple objects and must be allocated (factory rent, plant utilities, the production supervisor's salary). Direct material plus direct labor plus manufacturing overhead equals product cost.
Fixed vs variable vs mixed. Fixed costs do not change in total over the relevant range (straight-line depreciation, the lease on the plant, the salaried foreman).
Common mistakes
- Treating fixed cost per unit as constant. Fixed cost is constant in total over the relevant range. Per unit, it falls as volume rises and rises as volume falls. The exam will offer a choice that says "fixed cost per unit increases proportionally with production." Wrong.
- Confusing job order and process costing. Job order tracks costs by job; process tracks costs by department for a period. A custom yacht builder uses job order; a beverage bottler uses process.
- Mixing weighted average and FIFO equivalent units. Weighted average includes the work in beginning WIP at total cost and counts equivalent units of work completed plus equivalent units in ending WIP, beginning WIP is not subtracted.
Bottom line
- Costs sort four ways: direct vs indirect (traceability), fixed vs variable vs mixed (behavior), product vs period (timing), controllable vs uncontrollable (responsibility).
- Costing method follows production: job order for custom low-volume, process for homogeneous high-volume, ABC when overhead is large and diverse, joint/by-product allocation when one process yields multiple outputs.
- Weighted average equivalent units blend beginning WIP at total cost; FIFO counts only this-period work.
- ABC builds multiple cost pools and drivers, correcting the cross-subsidy single-rate allocation imposes between high-volume simple and low-volume complex products.
Exam shortcut
When a question describes a production environment, map the cue to the costing method: custom and distinct = job order, continuous and homogeneous = process, diverse overhead with multiple drivers = ABC, single process with multiple outputs = joint/by-product allocation.
The full lesson (about 5,090 words, 34 min read) adds 9 worked examples, all 5 common mistakes, a self-check, free in the app.
Learning objectives
- I.A3
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